A Hidden Reef Seven Times The Size Of NYC Behind The Great Barrier Reef

The Great Barrier Reef (GBR) is one of the most remarkable natural wonders of the world, which is why it’s such a catastrophe that climate change-induced ocean warming and acidification is systematically destroying it. Fortunately, after 30 years of mysterious signals and unconfirmed data points, a team of researchers have revealed that there is, in fact, another.

Specifically, just behind the GBR, a much deeper reef spanning an area of more than 6,000 square kilometers (2,316 square miles) has been found. That’s bigger than 7.5 New York Cities.

It is covered in donut-shaped mounds, each one measuring up to 300 meters (984 feet) across and 30 meters (98 feet) thick. These are comprised of organized growths of Halimeda, a commonplace green algae made from living, calcified sediments.

“We’ve known about these geological structures in the northern Great Barrier Reef since the 1970s and 80s, but never before has the true nature of their shape, size and vast scale been revealed,” study co-author Robin Beaman, a research fellow at James Cook University and expert in the GBR, said in a statement. “The deeper seafloor behind the familiar coral reefs amazed us.”

The new deep reef was thought to be fairly sizable, but this hidden cache is roughly three times the size of previous estimates. It stretches from just north of Port Douglas to the entire length of the Torres Strait.

Writing in the journal Coral Reefs, the team note that it was found using LiDAR, a surveying technology that uses lasers, instead of radio waves, to search for objects much in the way traditional radar does. In this case, it was deployed by aircraft from the Royal Australian Navy.

JCU News Release

And a bathymetric image of some Halimeda bioherms. Depths are coloured red (shallow) to blue (deep), over a depth range of about 50 metres:

A reef, but not a coral reef, although it may have once been so during lower sealevels.

What the heck do they mean by “behind”. Do they mean east or west?

West, I think. Could Ape Reef be on the left side of that image above?

One thing that has confused the heck out of me for several years is why the Great Barrier Reef proper is so narrow east to west. In other words, what is it about the easternmost edge of the Great Barrier Reef that kills off alomst all the coral to the west of it? Or to put it another way, why is the Great Barrier Reef so good at killing itself off? To illustrate, see how incredibly narrow Bligh Reef and Log Reef are in the image above.

mollwollfumble said:

What the heck do they mean by “behind”. Do they mean east or west?

West, I think. Could Ape Reef be on the left side of that image above?

One thing that has confused the heck out of me for several years is why the Great Barrier Reef proper is so narrow east to west. In other words, what is it about the easternmost edge of the Great Barrier Reef that kills off alomst all the coral to the west of it? Or to put it another way, why is the Great Barrier Reef so good at killing itself off? To illustrate, see how incredibly narrow Bligh Reef and Log Reef are in the image above.

The most active part of the reef is where the shallows drop off into deeper water. It is here that the tides and sea movement bring the nutrients for the coral polyps to eat, also water temperatures would be more stable and cooler.

PermeateFree said:

mollwollfumble said:

What the heck do they mean by “behind”. Do they mean east or west?

West, I think. Could Ape Reef be on the left side of that image above?

One thing that has confused the heck out of me for several years is why the Great Barrier Reef proper is so narrow east to west. In other words, what is it about the easternmost edge of the Great Barrier Reef that kills off alomst all the coral to the west of it? Or to put it another way, why is the Great Barrier Reef so good at killing itself off? To illustrate, see how incredibly narrow Bligh Reef and Log Reef are in the image above.

The most active part of the reef is where the shallows drop off into deeper water. It is here that the tides and sea movement bring the nutrients for the coral polyps to eat, also water temperatures would be more stable and cooler.

I’ve been reading in a textbook on Australian geology about the formation of reefs in general (eg Ningaloo) and the Great Barrier Reef in particular. And have figured out how coral came to be so good at killing itself off.

But first, the modern Great Barrier Reef is only 9,000 years old. That’s a blink of the eye in geological terms. The sea level has risen 26 metres since then, stabilising about 6,500 years ago. Long term coral growth occurs at a rate of 5 to 8 mm per year, so lagged badly behind the sea level rise. At the end of the 26 metres of sea level rise the coral of the Great Barrier Reef 14 metres below sea level, and didn’t reach the sea surface until 3,000 years ago. Since then the reef has spread sideways at an ever decreasing rate.

As for why the Great Barrier Reef is so good at killing itself, the answer is quite simple. Waves and parrot fish grind the reef coral into sand that builds up on the leeward face of the reef. Coral can’t grow on the resultant sand, and that is why the Great Barrier Reef is so thin side to side.